Washington -LRB- CNN -RRB- -- A week after the Supreme Court ruled in favor of an Ohio law that restricts early voting , Attorney General Eric Holder argued the decision will disproportionately affect African-Americans , many of whom `` heavily '' use early voting .

`` It is a major step backward to allow these reductions to early voting to go into effect , '' Holder said in a video message posted Monday .

`` Early voting is about much more than making it more convenient for people to exercise their civic responsibilities . It 's about preserving access and openness for every eligible voter , not just those who can afford to miss work or who can afford to pay for childcare , '' he continued in the video , which was posted on the Justice Department 's website .

The law cut down the state 's 35-day early voting window by seven days .

Proponents say that reducing in-person early voting would help create uniformity across the state 's counties , and voters would still be able to vote by mail during that seven-day window .

But critics argue the Republican-backed law will make it more difficult for minorities to vote .

Opinion : Why does GOP fight early voting ?

While the Justice Department was not a part of the lawsuit , it filed a brief in the case in July .

A federal judge had previously said the law was unconstitutional and placed a hold on it so it could n't go into effect . That decision was upheld by a federal appeals court judge . But the Supreme Court 's 5-4 decision allowed for the law to go into effect immediately . Early voting in Ohio now official starts this week .

In his video message , Holder said early voting is `` heavily used '' by African-Americans because the practice is popular among people who have a hard time getting to the polls due to childcare responsibilities , hourly salaries , and reduced access to transportation .

`` Restricting voting hours in ways that would disproportionately impact minority communities is not only unnecessary and unwarranted -- it is out of step with our history of continually expanding the franchise , '' he said . `` It is contrary to our fundamental values of equality , opportunity , and inclusion . And it is an affront to millions who have marched , and fought , and too often died to make real America 's most basic promise . ''

Holder announced late last month he 'll soon be resigning from his post , but will stay on until a replacement has been confirmed .

@highlight

Eric Holder blasts the Supreme Court 's ruling involving voting laws in Ohio

@highlight

The law limits the state 's 35 early voting window by seven days

@highlight

He and other critics say the law disproportionately affects minorities

@highlight

Proponents say it helps the state better line